A binary Mg-6Zn biodegradable alloy was solution treated to evaluate the effects of resulting microstructure changes on the alloy＇s degradation rate and mechanisms in-vitro. The treatment was conducted at 350 °C...A binary Mg-6Zn biodegradable alloy was solution treated to evaluate the effects of resulting microstructure changes on the alloy＇s degradation rate and mechanisms in-vitro. The treatment was conducted at 350 °C for 6-48 h. Optical and scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction were used to analyze the as-cast and treated samples. Immersion and electrochemical tests were performed in simulated body fluid at 37 °C to assess the samples corrosion resistance. To confirm the results of the corrosion tests, p H measurement was carried out. It is found that over 24 h solution treatment dissolves intermetallic phases in matrix and produces an almost single phase microstructure. Decreasing the intermetallic phases results in lower cathode/anode region ratios and lowers corrosion rates. The results of the electrochemical and mass loss tests reveal that extended solution treatment improves the corrosion resistance of the alloy. The results also show that solution at 350 °C for 24 h enhances the corrosion resistance of the as-cast alloy more than 60%. In addition, decreasing intermetallic phases in the microstructure accompanied a lower p H rise reduced corrosion rate. Solution treatment is suggested as a corrosion improving process for the application of Mg-Zn alloys as biodegradable implant materials.展开更多
AIM: To provide the useful information for the diagnosis of liver cirrhosis by observing the morphology of peripheral hepatic vessels and the hemodynamics of microbubble arrival time in these vessels.METHODS: Twenty-o...AIM: To provide the useful information for the diagnosis of liver cirrhosis by observing the morphology of peripheral hepatic vessels and the hemodynamics of microbubble arrival time in these vessels.METHODS: Twenty-one subjects including 5 normal volunteers and 16 patients (liver cirrhosis, n=10;chronic hepatitis, n=6) were studied by contrast-enhanced coded phase inversion harmonic sonography (GE LOGIQ9 series) using a 6-8 MHz convex-arrayed wide-band transducer. The images of peripheral hepatic artery,portal and hepatic vein were observed in real-time for about 2 min after intravenous injection of Levovist. The time when microbubbles appeared in the peripheral vessels (microbubble arrival time) was also recorded. The morphologic changes of peripheral hepatic vasculature were classified as marked, slight, and no changes based on the regularity in caliber, course, ramification, and the delineation of vessels compared to normal subjects.RESULTS: The microbubble arrival time at peripheral artery, portal, and hepatic vein was shorter in cirrhotic patients than in chronic hepatitis patients and normal subjects. The marked, slight and no morphologic changes of peripheral hepatic vasculature found in 5 (5/6,83.3%), 1 (1/6, 16.7% ), and 0 (0/6, 0%) liver cirrhosis patients, respectively, and in 1 (1/10, 10%), 6 (6/10,60%), and 3 (3/10, 30%) chronic hepatitis patients,respectively. There was a significant difference between the two groups (P＜0.001).CONCLUSION: Evaluation of the hemodynamics and morphology of peripheral hepatic vasculature by contrast-enhanced coded pulse inversion harmonic sonography can provide useful information for the diagnosis of liver cirrhosis.展开更多
Dissimilar friction stir welding （FSW） of copper and aluminum was investigated by nine different tool designs, while the rest of the process parameters were kept constant. Mechanical and metallurgical tests such as ...Dissimilar friction stir welding （FSW） of copper and aluminum was investigated by nine different tool designs, while the rest of the process parameters were kept constant. Mechanical and metallurgical tests such as macrostructure, microstructure, tensile test, hardness, scanning electron microscope and electron X-ray spectrographs were performed to assess the properties of dissimilar joints. The results exhibited that, the maximum joint strength was achieved by the tool of cylindrical pin profile having 8 mm pin diameter. Besides, the fragmental defects increased as the number of polygonal edges decreased, hence the polygonal pin profiles were unsuitable for dissimilar FSW butt joints. Furthermore, the tensile strength increased as the number of polygonal edges increased. Stir zone of polygonal pin profiles was hard and brittle relative to cylindrical tool pin profiles for same shoulder surface. Maximum hardness of HV 283 was obtained at weld made by the polygonal square pin profile. The hard and brittle intermetallic compounds （IMCs） were prominently presented in the stir zone. Phases of IMCs such as CuAl, CuAl2, Cu3Al and Cu9Al4 were presented in the stir zone of dissimilar Cu-Al joints.展开更多
When the frigate moves forward,due to the ship motion such as pitching and rolling,the flow over the flight deck becomes very complex,which may seriously threaten the taking off and landing of the ship-borne helicopte...When the frigate moves forward,due to the ship motion such as pitching and rolling,the flow over the flight deck becomes very complex,which may seriously threaten the taking off and landing of the ship-borne helicopter.The flow fields over the different modified simple frigate shape(SFS)models,consisting of the hangar and flight deck,were numerically studied by changing the ratio of hangar height and length in the static state and pitching state.For different models,the contours of velocity and pressure above the flight deck,as well as the variations of velocity components of the observation points and line in static state and pitching state were compared and analyzed.The results show that the size of recirculation zone and the location of the reattachment point have distinct differences for diverse models,and reveal the tracks of recirculation zone’s center and reattachment position in a pitching period.In addition,the velocity components at two observation positions also change periodically with the periodic motion.Furthermore,the deviations of the velocity components in static state and pitching state are relatively large,therefore,the flow fields in static state cannot be used to simulate that in pitching state correctly.展开更多
Neuroendocrine carcinomas(NEC) of the pancreas are defined by a mitotic count > 20 mitoses/10 high power fields and/or Ki67 index > 20%, and included all the tumors previously classified as poorly differentiated...Neuroendocrine carcinomas(NEC) of the pancreas are defined by a mitotic count > 20 mitoses/10 high power fields and/or Ki67 index > 20%, and included all the tumors previously classified as poorly differentiated endocrine carcinomas. These latter are aggressive malignancies with a high propensity for distant metastases and poor prognosis, and they can be further divided into small- and large-cell subtypes. However in the NEC category are included also neuroendocrine tumors with a well differentiated morphology but ki67 index > 20%. This category is associated with better prognosis and does not significantly respond to cisplatin-based chemotherapy, which represents the gold standard therapeutic approach for poorly differentiated NEC. In this review, the differences between well differentiated and poorly differentiated NEC are discussed considering both pathology, imaging features, treatment and prognostic implications. Diagnostic and therapeutic flowcharts are proposed. The need for a revision of current classification system is stressed being well differentiated NEC a more indolent disease compared to poorly differentiated tumors.展开更多
基金the Ministry of Higher Education of Malaysia for the financial support (Vote No. Q.J130000.2524.04H18)Faculty of Mechanical Engineering of Universiti Teknologi Malaysia (UTM) for providing research facilities
文摘A binary Mg-6Zn biodegradable alloy was solution treated to evaluate the effects of resulting microstructure changes on the alloy＇s degradation rate and mechanisms in-vitro. The treatment was conducted at 350 °C for 6-48 h. Optical and scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction were used to analyze the as-cast and treated samples. Immersion and electrochemical tests were performed in simulated body fluid at 37 °C to assess the samples corrosion resistance. To confirm the results of the corrosion tests, p H measurement was carried out. It is found that over 24 h solution treatment dissolves intermetallic phases in matrix and produces an almost single phase microstructure. Decreasing the intermetallic phases results in lower cathode/anode region ratios and lowers corrosion rates. The results of the electrochemical and mass loss tests reveal that extended solution treatment improves the corrosion resistance of the alloy. The results also show that solution at 350 °C for 24 h enhances the corrosion resistance of the as-cast alloy more than 60%. In addition, decreasing intermetallic phases in the microstructure accompanied a lower p H rise reduced corrosion rate. Solution treatment is suggested as a corrosion improving process for the application of Mg-Zn alloys as biodegradable implant materials.
文摘AIM: To provide the useful information for the diagnosis of liver cirrhosis by observing the morphology of peripheral hepatic vessels and the hemodynamics of microbubble arrival time in these vessels.METHODS: Twenty-one subjects including 5 normal volunteers and 16 patients (liver cirrhosis, n=10;chronic hepatitis, n=6) were studied by contrast-enhanced coded phase inversion harmonic sonography (GE LOGIQ9 series) using a 6-8 MHz convex-arrayed wide-band transducer. The images of peripheral hepatic artery,portal and hepatic vein were observed in real-time for about 2 min after intravenous injection of Levovist. The time when microbubbles appeared in the peripheral vessels (microbubble arrival time) was also recorded. The morphologic changes of peripheral hepatic vasculature were classified as marked, slight, and no changes based on the regularity in caliber, course, ramification, and the delineation of vessels compared to normal subjects.RESULTS: The microbubble arrival time at peripheral artery, portal, and hepatic vein was shorter in cirrhotic patients than in chronic hepatitis patients and normal subjects. The marked, slight and no morphologic changes of peripheral hepatic vasculature found in 5 (5/6,83.3%), 1 (1/6, 16.7% ), and 0 (0/6, 0%) liver cirrhosis patients, respectively, and in 1 (1/10, 10%), 6 (6/10,60%), and 3 (3/10, 30%) chronic hepatitis patients,respectively. There was a significant difference between the two groups (P＜0.001).CONCLUSION: Evaluation of the hemodynamics and morphology of peripheral hepatic vasculature by contrast-enhanced coded pulse inversion harmonic sonography can provide useful information for the diagnosis of liver cirrhosis.
基金funding support provided by the Board of Research in Fusion Science and Technology(BRFST)Gandhinagar and Office of Research and Sponsored Projects(ORSP)Pandit Deendayal Petroleum University(PDPU),Gandhinagar under projects of NFP/MAT/A 10/04 and ORSP/R&D/SRP/2014/RDKM respectively
文摘Dissimilar friction stir welding （FSW） of copper and aluminum was investigated by nine different tool designs, while the rest of the process parameters were kept constant. Mechanical and metallurgical tests such as macrostructure, microstructure, tensile test, hardness, scanning electron microscope and electron X-ray spectrographs were performed to assess the properties of dissimilar joints. The results exhibited that, the maximum joint strength was achieved by the tool of cylindrical pin profile having 8 mm pin diameter. Besides, the fragmental defects increased as the number of polygonal edges decreased, hence the polygonal pin profiles were unsuitable for dissimilar FSW butt joints. Furthermore, the tensile strength increased as the number of polygonal edges increased. Stir zone of polygonal pin profiles was hard and brittle relative to cylindrical tool pin profiles for same shoulder surface. Maximum hardness of HV 283 was obtained at weld made by the polygonal square pin profile. The hard and brittle intermetallic compounds （IMCs） were prominently presented in the stir zone. Phases of IMCs such as CuAl, CuAl2, Cu3Al and Cu9Al4 were presented in the stir zone of dissimilar Cu-Al joints.
基金supported by the Fundamental Research Funds for the Central Universities(No. NS2019006)the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD)
文摘When the frigate moves forward,due to the ship motion such as pitching and rolling,the flow over the flight deck becomes very complex,which may seriously threaten the taking off and landing of the ship-borne helicopter.The flow fields over the different modified simple frigate shape(SFS)models,consisting of the hangar and flight deck,were numerically studied by changing the ratio of hangar height and length in the static state and pitching state.For different models,the contours of velocity and pressure above the flight deck,as well as the variations of velocity components of the observation points and line in static state and pitching state were compared and analyzed.The results show that the size of recirculation zone and the location of the reattachment point have distinct differences for diverse models,and reveal the tracks of recirculation zone’s center and reattachment position in a pitching period.In addition,the velocity components at two observation positions also change periodically with the periodic motion.Furthermore,the deviations of the velocity components in static state and pitching state are relatively large,therefore,the flow fields in static state cannot be used to simulate that in pitching state correctly.
文摘Neuroendocrine carcinomas(NEC) of the pancreas are defined by a mitotic count > 20 mitoses/10 high power fields and/or Ki67 index > 20%, and included all the tumors previously classified as poorly differentiated endocrine carcinomas. These latter are aggressive malignancies with a high propensity for distant metastases and poor prognosis, and they can be further divided into small- and large-cell subtypes. However in the NEC category are included also neuroendocrine tumors with a well differentiated morphology but ki67 index > 20%. This category is associated with better prognosis and does not significantly respond to cisplatin-based chemotherapy, which represents the gold standard therapeutic approach for poorly differentiated NEC. In this review, the differences between well differentiated and poorly differentiated NEC are discussed considering both pathology, imaging features, treatment and prognostic implications. Diagnostic and therapeutic flowcharts are proposed. The need for a revision of current classification system is stressed being well differentiated NEC a more indolent disease compared to poorly differentiated tumors.
